1. Field of the Invention
The present invention relates to a producing method of a wired circuit board and, more particularly, to a producing method of a wired circuit board such as a flexible wired circuit board.
2. Description of the Related Art
A wired circuit board such as a flexible wired circuit board has an insulating base layer, a conductive pattern formed thereon, and an insulating cover layer formed on the insulating base layer so as to cover the conductive pattern. It has been known that, in the production of such a wired circuit board, an insulating base layer, a conductive pattern, and an insulating cover layer are successively formed, and then the shape of the conductive pattern is optically inspected for a defect.
For example, as shown in FIG. 5, it has been proposed that a wired circuit board 40 including an insulating base layer 42, a conductive pattern 41, and an insulating cover layer 45 is placed on the upper surface of a support table 44 made of metal, and then light is applied to the wired circuit board 40 from thereabove to conduct an inspection of the conductive pattern 41 with reflected light which is the light reflected by the wired circuit board 40 (see, e.g., Japanese Unexamined Patent No. 2006-112845).
Specifically, pattern reflected light 51 which is the light reflected by the conductive pattern 41 via the insulating cover layer 45 and table reflected light 52 which is the light reflected by the support table 44 via the insulating cover layer 45 and the insulating base layer 42 exposed from the conductive pattern 41 are each sensed as the reflected light with a CCD camera.
In the inspection of the conductive pattern 41 described in Japanese Unexamined Patent No. 2006-112845, the difference between an amount of the pattern reflected light 51 and an amount of the table reflected light 52, i.e., the contrast (brightness difference) therebetween is used to recognize the shape of the conductive pattern 41, and determine whether or not the shape of the conductive pattern 41 is defective.
In the inspection of Japanese Unexamined Patent No. 2006-112845, there is the problem that, when the contrast between the pattern reflected light 51 and the table reflected light 52 is low, the shape of the conductive pattern 41 is difficult to recognize. To solve such a problem, it has been proposed that the reflectance of the table reflected light 52 is reduced to a value of not more than 10% to ensure a high contrast between the pattern reflected light 51 and the table reflected light 52.
On the other hand, it has been conventionally proposed that, in the production of a wired circuit board, a foreign matter present on a conductive pattern is inspected (see, e.g., Japanese Unexamined Patent No. 11-307883).
Specifically, as indicated by the solid line of FIG. 5, the reflectance of foreign-matter reflected light 53 which is the light reflected by a foreign matter 46 via the insulating cover layer 45 is low when the foreign matter 46 is made of a resin material such as rubber. Accordingly, the foreign matter 46 present on the conductive pattern 41 is inspected by ensuring a high contrast between the foreign-matter reflected light 53 and the pattern reflected light 51.